Such drive trains are used in power plant vehicles. The automatically operated transmissions are thereby controlled by means of actuators. In case of a mechanical defect or of a defect of the transmission control, the vehicle can inadvertently accelerate to high rotational speeds and/or constituent parts of the transmission and/or a clutch disposed between the internal combustion engine and transmission.
It was already provided in such drive trains that the torque of the internal combustion engine present at the transmission be reduced in the event of a defect. Such a measure only intervenes in a limited manner to reduce the vehicle speed because the drag torque of the internal combustion engine thus caused by the reduction of torque and an open clutch between the internal combustion engine and transmission becomes ineffective.